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I am getting stripes in the sky after developing 8x10 KODAK 160Vc colour plates with the TETENAL COLORTEC C-41 kit and a CPA-2 JOBO rotary processor with a 3005 drum. I am doing exactly as the instruction say: 38º temperature, position P in the processor (50 r.p.m.), 3´15´´ development time. A quicker speed (75 r.p.m) would perhaps solve this problem? What other factor can cause this uneven development?
Not enough chemicals? What kind of stripes ?
I have a similar setup of Jobo equipment for 4x5 and 8x10 and experienced a similar problem. Since Jobo recommends a slower speed (50 rpm) for the larger expert drums, you should use more than the minimum amount of chemistry shown on the drum. The other thing to check is whether the tank is level (end to end) when rotating on the processor. This will also cause uneven development especially when using less chemistry.
Try calling Lightwaves, a professional C-41 lab in San Francisco http://www.lightwavesimaging.com. They have found that 8x10 film will streak if not properly agitated and offer "exhibition processing" to eliminate the problem. You might call and ask what they are doing......if they will give up any trade secrets?
I am not shure this is any help, but when I had a ATL 1000/1500 (not being able to use expert tanks) and tried to develop ektachrome 8"x10" in a JOBO 2800-series paper drum, I got a magenta color cast visible in the low density areas of the slide. I never had that trouble with the Fujichrome 8"x10" (cold-stored stuff from freestyle of course..) developed in the same Jobo-drum. Answers I got in this forum explained that the reason for this color cast with ektachrome 8"x10" (uneven magenta/pink areas) were unsuficient washing of base side of sheet were a anti-halo backing were to be washed of during developement. Is this an issue with Your film as it is clearly different for different films?. Also, I know that some users of the expert drum express that it may be necessary to have a larger developer quantity than the stated minimum to get identical wetting/developement of prints. I have used my 4 sheet 3004 (memory... - but it is the expert tank that can take 4 sheets 10"x12") expert tank for developing 2x4 sheets of 5x7 (actually half-plate size Velvia) simultanously in E6 -3 bath tetenal with 300ccm of chemistry getting uniform result. I use an ATL 3000, but I run it at 25 RPM.
I don't know if this will help with your particular problem, but I have noted inconsistent processing in a Jobo 3005 tank too. I now load the tank so that the film is placed into each "tube" so that the open end is closest to the center of the drum and haven't had a problem with inconsistency. If that doesn't help, give Jobo tech support a call as thay can probably help. Good luck!
Regards, Pete
Carlos
Are the stripes , two vertical or horizontal dark bands evenely spaced on the film ???
They would show up as minus density on negative and produce very dark obvious bands in the print:??
If so this problem has plagued me for 1 full year. It only showed up in D76 or Tmax not pyro.
nuetral background or large areas of nuetral sky would be the obvious areas.
We tried every combination to solve this problem, the marks look like large road rutts in the print, tried at least 30 runs of film to solve the problem, from changing water , pre soak , heating drum before running . three different speeds on the jobo, location of jobo, checking for a voltage problem on the processor.
Finally we solved the problem,
By the way the problem only showed itself with 120 or 22o film.
We now start the run, and immediately after the chemical is in the drum, we manually take the tank off the Jobo and give a traditional inversion of the tank, we put the tank back on machine for one rotation, then take off again and manually invert the tank again, this is done three times within the first minute of development.
The problem is eliminated
I know Jobo would not say this is right but I can tell you, we almost stopped running 120 film in the jobo as a result of the road rutts that we saw in the nuetral skys and backgrounds(complicated images or backgrounds would not show the obvious problem)
I don,'t know if this helps but I do know it works and will eliminate the stripes or road rutts.